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Transplanted Brain Cells May Suffer From Parkinson's `Spread'

- Apr 06 2008

By Tom Randall and Elizabeth Lopatto

Brain damage linked to Parkinson's disease may spread into transplanted tissue, diminishing hopes of permanent relief through such treatments, according to studies published today in the journal Nature Medicine.

Two groups working independently, one from Wallenberg Neuroscience Center in Lund, Sweden, and one from Rush University Medical Center in Chicago, saw signs of the disease in healthy transplants grafted to damaged tissue. A third study at Harvard Medical School in Boston and Dalhousie University in Halifax, Canada, showed the opposite.

There is no cure for Parkinson's disease, which affects the parts of the brain that control movement, leading to trembling hands, slowed mobility and poor balance. Cell transplants have been shown to help some patients in previous studies, though long-term effectiveness hasn't been established, researchers said. The findings raise questions about whether stem cells can cure Parkinson's, researchers said.

"Our results suggest that grafted cells can be affected by the disease process and thereby might limit the long-term clinical benefit of these treatment approaches,'' according to the authors of the Rush University study. ``It is unclear whether a similar fate would befall stem cell grafts, the next generation of cell replacement procedures.''

The Swedish study was of two people who had fetal nerve tissue grafted to their brains. Though the grafts survived 16 years in these patients, they showed abnormal clumps of proteins called Lewy bodies that are characteristic of Parkinson's disease. Despite this, patients still seemed to experience relief from symptoms, the researchers wrote.

Initial Improvement

In the Rush University study, researchers examined the brain of the longest-surviving graft patient, a woman who died at age 61, about 14 years after healthy nerve cells had been transplanted to the brain. The patient's movements had initially improved after the graft and she needed fewer doses of medicine to keep the disease at bay.

After some years of improvement, the patient's symptoms worsened until her death from a heart attack in 2007. Her brain had also developed "Lewy-body-like'' areas showing that, like the patients in the Swedish study, the Parkinson's disease had extended to the grafted cells and continued to spread until death.

The Harvard study analyzed five patients at nine to 14 years after their transplants. This study showed that the grafted nerve cells survived up to 14 years without deterioration. That result may be due to different methods used to transplant the cells, and the results support future experimentation with stem cells, researchers said.

People with Parkinson's usually begin to show symptoms about age 60. About 1 in 100 people of that age or older have the disease, according to the National Parkinson Foundation, an advocacy group. It can also be diagnosed in younger people, most famously in Michael J. Fox, who was diagnosed at age 30 in 1991 and told the public in 1998.

Patients are currently treated with levodopa, which is converted into the chemical dopamine in the brain. This relieves Parkinson's symptoms, according to the Mayo Clinic.